If you do a search here, there are even some threads on this very topic. Being in CO, you're in a similar boat as mine in Iowa. I did quite a bit of research before I started finishing my basement, and in the end I liked what I found at Building Science Corporation
. Last I knew the PDF that I used that had a ton of excellent info in it is gone from their site, but I think it can still be found on the net. If you can't find, I can probably scrounge it up.
Basically, what they found through lots of site surveys (empirical data) was that in colder climates the old 'interior vapor barrior/insulation/concrete' concept doesn't work as well in practice as it would seem in theory. There's way too much to go into here, but essentially, the problem goes like this:
During the heating season, you have very cold concrete - sometimes extremely cold. You have lots of penetrations in the vapor barrier (outlets, switches, etc.) where warm humid air inevitably enters the wall cavity. That warm vapor travels away from the conditioned space toward the cold foundation (thermodynamics says so) where it condenses. Now you have condensation in an insulated space. You need heat and air to vaporize the condensation - which won't ever happen efficiently because the cavity is insulated! Then, the problem is compounded if you have water intrusion - it can get in, but it can't get out.
What Building Science Corp recommended (from memory) was no interior vapor barrier, unfaced insulation, and an XPS (closed-cell) board (which is a vapor retarder) against the foundation. The lack of vapor barrier allows the wall to dry to the interior, but the XPS raises the temperature inside the wall assembly enough (even in extreme cold) that condensation shouldn't occur. If it does, or if there is water intrusion from the exterior, the assembly can dry.
Of course, this is academic and so probably wouldn't pass code in many locales. The concept makes perfect sense to me, though and certainly wouldn't be the first time public policy wasn't the best way to accomplish something.http://buildingscience.com/
Note - there are lots of schools of thought on this subject and as others have mentioned, it also depends on your climate and local building codes. Do your homework.
Sorry for the long post.